1. Field of the Invention
The invention is directed to an improved valve for controlling a communication in a high-pressure fluid system, in particular in a fuel injection system for an internal combustion engine.
2. Description of the Prior Art
One valve of the type with which this invention is concerned, known from European Patent Disclosure EP 0 840 003 A, serves to control a communication in a fuel injection system for an internal combustion engine. The valve has a valve member, which is guided displaceably in the direction of its longitudinal axis and protrudes into a pressure chamber, and which in the pressure chamber has a sealing face, on a face end disposed transversely to its longitudinal axis. The valve member, with its sealing face, cooperates with a valve seat, disposed transversely to its longitudinal axis, for closing off an opening, surrounded by the valve seat, from the pressure chamber. High pressure prevails in the pressure chamber, and the opening leads to a relief chamber, and the communication of the pressure chamber with the relief chamber and thus the pressure in the pressure chamber are controlled by the valve member. To achieve secure sealing off of the opening from the pressure chamber, a high pressure per unit of surface area of the sealing face on the valve seat is needed. To limit the requisite contact pressure of the valve member on the valve seat to a magnitude that can still be controlled, it is necessary to embody the sealing face with the smallest possible surface area. Because of the impact load that occurs when the valve member, with its sealing face, strikes the valve seat, damage to the sealing face can easily occur, in the form of broken-out places. Through these broken-out places, fluid from the pressure chamber can flow out via the opening. Because of the high pressure difference, very high flow velocities occur, which leads to erosion, or in other words a removal of material from the valve member, thus enlarging the broken-out places. As a result, with increasing time in use of the valve, the sealing action becomes poorer, and finally the valve is no longer functional. Because of production variations in the valve member and/or the valve seat, small through openings may also be present between the sealing face and the valve seat, which as indicated above enlarge over the time in use of the valve and lead to functional failure.
The valve according to the invention has the advantage over the prior art that the valve function is assured even over a long time in use of the valve. By means of the apertures of the valve member, a slight leakage is brought about intentionally, but this is not significant to the function of the valve, and by means of the annular face, it is attained that when fluid flows out of the pressure chamber, only a low flow velocity occurs, and so there is not erosion of the valve member or the valve seat. The valve thus has only slight overall leakage, which, however, remains at least approximately constant over the time in use.
Various advantageous features and refinements of the valve of the invention are disclosed. One embodiment makes a simple embodiment of the apertures possible. Another embodiment makes a low flow velocity of the fluid flowing out of the pressure chamber possible and the flow velocity of the outflowing fluid may be made at least approximately constant. A further embodiment makes simple production of the valve member possible.